The invention relates to a temperable glass coating according to the preamble of patent claim 1.
Coatings on transparent glass or transparent synthetic material serve to reflect or absorb specific wavelengths or wavelength ranges of incident light. Known are coatings on optical lenses and on window panes, also referred to as architectural glass, as well as the coatings on motor vehicle window panes.
The most important function of a coating on architectural glass is the reflection of thermal radiation in order for a room not to become too warm during the summer and not too cool during the winter. In the process the visible light is to be minimally weakened, i.e. the coating should have high transmission in the visible range (approximately 400 nm to 700 nm under daylight vision and approximately 390 nm to 650 nm under night vision) and high reflection for thermal and infrared radiation (wavelength>700 nm).
Layer systems fulfilling this function are referred to as low-E layer systems, “E” representing emissivity (=degree of emission or emission capability). This is intended to express that these layer systems only output low thermal radiation from a building room to the outside.
As a rule, heat regulation is attained thereby that onto glass electrically high-conducting layers are applied, frequently comprising a metal such as Cu, Ag, Au with a very low radiation emission coefficient.
Due to the light reflection of these low-E layers, which is often too high, these layers are sometimes antireflection-coated with the aid of additional transparent layers. By applying the transparent layers, the desired color tint of the glass pane can also be set.
A coated substrate is already known which comprises at least one metallic coating layer and further dielectric layers (EP 1 089 941 B1). This coated substrate is structured such that it can be tempered and bent.
A substrate provided with a multilayer system is furthermore known which is also temperable and bendable (U.S. Pat. No. 6,576,349 B2, U.S. Pat. No. 6,686,050 B2). The multilayer system utilized herein comprises two layers which reflect infrared radiation and which are each encompassed by two NiCrOx layers.
Further, a heat-insulating layer system is known which, after the coating, is tempered and bent (DE 198 50 023 A1 or EP 0 999 192 B1). This layer system comprises a precious metal layer disposed on a TiO2 layer, the two layers being encompassed by suboxidic NiCrO2.
Lastly, temperable coatings are also known which utilize substoichiometric SixNy or SiNxOy (WO 2005/19127 A1, WO 2005/034192 A2).
The different layers are, as a rule, produced with the aid of sputter processes, in which by means of positive ions particles are knocked out of so-called targets, which particles are subsequently deposited on the substrate, which may be architectural glass.
The known layer systems entail at least one of the following cited disadvantages:
expensive or exotic starting materials for sputter targets
complex and complicated process control
complex layer structuring
inadequate optical properties
severe changes of the essential properties of the coated glass by a temper process.
The invention addresses the problem of providing a simple and cost-effective silver low-E coating, which only minimally changes its essential properties after tempering.